Spectral components above the useful frequency range of a stereo multiplex signal signify noise in the reception of the stereo multiplex signal, which, without further measures, are noticeable as audible noise in the reproduced audio signals. Thus, for example, the ignition spark of an internal combustion engine transmits short high-frequency pulses within a broad frequency range, which results in the aforementioned spectral components in the stereo multiplex signal. Therefore circuit arrangements are known, especially for car radios, which influence the audio signals in a suitable manner depending on the appearance of such spectral components, for example, by sustaining for a short period an amplitude that was present prior to the appearance of the noise.
The object of the present invention is to provide a circuit arrangement, which advantageously obtains those spectral components of the multiplex signal which indicate noise (interference), the requirements of digital signal processing having to be taken into account, in particular--for example a lowest possible requirement for computing power.